Significant resources have been invested in HIV testing to date, yet over half of adults globally remain unaware of their HIV status. Men in particular fall well below international HIV testing targets and those at highest risk of HIV infection are often the least likely to participate in community-based mobile HIV testing efforts. HIV- infected men also link to care at lower rates than women. Both the male testing and linkage to care gaps pose a challenge for the implementation of combination HIV prevention strategies, including treatment as prevention (TasP). Identifying interventions to increase HIV testing among men - particularly those engaged in high-risk behaviors - is thus an HIV prevention priority in sub-Saharan Africa. Although economic incentives - the offer of economic rewards that are conditional on undertaking a certain action - have been found to be effective in modifying health behaviors in low-income countries, existing approaches to incentives have failed to incorporate prominent insights from behavioral economics, leaving room for smarter incentive-based interventions that can be more effective and less expensive in increasing uptake of HIV testing and linkage to care. The long-term sustainability and cost-effectiveness of such interventions have also yet to be clearly established. This study will implement and evaluate novel incentive-based interventions to increase HIV testing among high-risk men and link HIV-infected adults to treatment. Aim 1 will build on insights from behavioral economics theories and studies, and test the premises that (1) incentives in the form of lotteries, with smal probabilities of winning high-value prizes as a result of HIV testing, may be more powerful than small, fixed incentives for HIV testing; and (2) individuals display loss aversion (a reluctance t lose something they already own) and therefore are less motivated by the possibility of gaining something from HIV testing (i.e. a standard fixed incentive) than the possibility of losing something from not testing. The lottery-based incentives are likely to be most appealing to individuals with risk-seeking preferences, thereby ensuring that HIV testing is promoted in a targeted and inexpensive manner. Lottery and loss aversion-based incentives will be compared to fixed incentives, in a three-arm, randomized controlled trial. Aim 2 will draw upon the existence of loss aversion in individuals' decision-making patterns to examine whether men who test HIV-positive are more likely to link to care if the incentive offered to them features a saliet, immediate benefit to early linkage. Aim 3 will assess the sustainability and cost-effectiveness of novel economic incentives to increase testing by analyzing the effect of one-time incentives on subsequent HIV testing when incentives are no longer offered. The study will advance the scientific understanding of how and why incentives influence decision-making while also identifying low-cost, sustainable ways to increase demand for HIV testing among high-risk individuals, improve linkage to care, and ultimately facilitate the implementation of combination HIV prevention strategies.